1. Field of the Invention
The invention relates to test switch and pilot light structures generally and particularly to a test switch/pilot light having a light emitting diode which is shorted by a switch, lamping of an emergency fluorescent lighting fixture or the like providing illumination at reduced levels, thereby to test visually the operational worthiness of an inverter unit.
2. Description of the Prior Art
Fluorescent lighting fixtures of various description including such fixtures generally known as linear fixtures and downlighting fixtures can be provided with battery packs and associated circuitry which operate fluorescent lamping of the fixtures for a minimum period of time on interruption of normal power. Such devices are generally referred to as inverter units, battery/inverter units, or battery/charger board units and will be referred to herein as an inverter unit. Units with which the present test switch can be employed also include ballast load transfer devices and the like which do not include batteries. The present test switch can be used as a remote test switch with any number of emergency lighting fixtures. Present day inverter units often carry maintenance-free, high-temperature nickel-cadmium batteries within sealed housings formed of high impact polycarbonate polymers or steel. Such inverter units are described, for,.example, in U.S. Pat. Nos. 5,202,608 and 5,814,971. Lithonia Lighting, a division of National Service Industries, Inc., of Atlanta, Ga., manufactures and markets inverter units of this type under the POWER SENTRY trademark for particular use with linear fluorescent fixtures and downlighting fluorescent fixtures and particularly such fixtures used in office and industrial environments. Linear fluorescent fixtures such as are manufactured by Lithonia Lighting are known under the designations OPTIMAX; 2PM3N, and GT/SP which identify respectively parabolic troffer fixtures and lensed troffer fixtures which are particularly configured to drive linear fluorescent lamping of the T12 or T8 type, for example. In downlighting fluorescent fixtures, inverter units typically operate compact fluorescent lamps of varying description via the agency of nickel-cadmium batteries permanently sealed within steel enclosures.
Test switches have long been used in lighting systems including emergency lighting function such that the condition and operational worthiness of inverter units can be quickly and conveniently determined. In normal operation, a visual signal is usually provided by a light emitting diode which gives off light once the unit is connected to power. Operation of a prior test switch in this environment causes the LED to be extinguished for as long as the test is underway. Prior test switches have included manually operable switch elements which allow inverter units to be tested by reference to a visual signal, such prior test switches having taken other structural configurations than those of the test switches of the present invention and have particularly been more costly to manufacture. In particular, prior test switches of this type have included LED""s and switches in completely separate housings. Other prior test switches have included separate toggle switches and panel-mounted light emitting diodes with further inclusion of structure such as PCB-mounted dome switches with PCB-mounted light emitting diodes. Essentially all such prior devices use a dedicated switch such as a PCB-mounted dome switch to complete a circuit. A particular feature of the present test switches which yield substantial utility in manufacture and assembly is the provision of a switch housing which can essentially be unitarily formed from a polymeric material and which houses an LED and a contact which can be brought into engagement with leads of the LED to provide a visual signal evidenced by continuing lamp operation at reduced output to indicate proper inverter operation. The LED is actually shorted and goes out. The structure so envisioned can be rapidly assembled from a minimum of parts, the resulting structure being capable of remote disposition, for example, a few feet or so, from the inverter unit and lighting fixture so that testing is facilitated. The present invention therefore provides improved test switch assemblies which also include connector structure tied to the switch housing for mounting of the test switch to a portion of the lighting fixture. The assemblies of the present invention also provide structure capable of mounting into a variety of materials such as castings, sheet metal, plastic, etc., over a range of thicknesses with ease and rapidity. The invention thus contemplates improvement over the prior art by way of providing an inexpensive and compact structure having a minimum of parts and which is readily manufactured and assembled at minimum cost.
The invention provides embodiments of a test switch and mounting assembly which is particularly useful as a manual switch to determine the condition of an inverter unit used to, provide an emergency lighting capability in fluorescent lighting fixtures. In both linear and downlighting fluorescent lighting fixtures, an emergency capability is provided by means of a sealed inverter housing containing batteries capable of driving fluorescent lamping at a fractional output of full lumen rating to yield optimum, glare-free emergency illumination for a minimum period of time on interruption of normal AC mains power. Inverter units useful in such applications are manufactured and marketed by Lithonia Lighting, a division of National Service Industries, Inc., of Atlanta, Ga., certain examples of the inverter units manufactured by Lithonia being proprietary and being the subjects of U.S. Pat. Nos. 5,202,608 and 5,814,971, the disclosures of which patents are incorporated hereinto by reference. Inverter units useful for providing an emergency lighting capability to both linear and downlighting fluorescent fixtures are marketed by Lithonia Lighting under the trademark designation of POWER SENTRY.
The batteries contained within inverter units must be capable of being tested periodically in order to ascertain the condition of the batteries, that is, to determine whether the batteries are sufficiently charged to possess the capability of driving lamping during an emergency occasioned by a power failure. Testing of associated inverter circuitry is also necessary. Embodiments of manually operable test switches configured according to the invention replace conventional test switches used in a similar manner to determine the operational worthiness of inverter units as has been described herein. The present test switches can be inexpensively manufactured relative to the cost of prior switches while retaining all capabilities of prior switches. In manufacture of the present switches, fewer parts are required and those parts can be individually manufactured at reduced cost. Assembly of the several component parts of the present test switches can be more rapidly accomplished in a typical manufacturing environment than those switches of the prior art which are replaced by the present test switches.
The present test switches are provided with polymeric housings, typically clear, xe2x80x9cplasticxe2x80x9d housings having opposing housing portions joined together along one edge for movement relative to each other in the manner of a xe2x80x9cliving hingexe2x80x9d such that the housing portions can be snapped together once internal switch components have been placed inside the housing. The housings of the present switches are further provided with a connector held to the housing by means of a connecting tie integrally formed of plastic material and molded with the housing and the connector simultaneously. Lengths of cable connect a light emitting diode disposed internally of any one of the several housings, exterior ends of the cable being electrically connected to a molded connector formed of plastic material, the molded connector having internally disposed electrical contacts which mate with contacts located within an inverter unit. The inverter unit is provided with an opening through which a conventional electrical harness extends, the harness having a mating connector which joins to the test switch of the invention in order to form an electrical circuit with internal circuit elements of one of the inverter units.
According to the several embodiments of the invention, a substantially box-like housing has a cylindrical housing element formed at one end thereof, the cylindrical housing element receiving a plastic plunger element which can be biased downwardly by finger pressure exerted against portions of the plunger which extend from the cylindrical housing element. Displacement of this plunger causes an electrical contact to complete a circuit with leads emanating from the light emitting diode and joined to the electrical cables which connect with elements to be tested disposed internally of one of the inverter units through the connector mentioned above. The light emitting diode is thus de-energized and the fluorescent tamping is caused to operate at a reduced output, thereby providing an indication of the operational worthiness of the inverter unit. In the event that the condition of the inverter unit is inadequate to provide the necessary emergency lighting function, the fluorescent tamping will not illuminate on operation of the test switch. The test switch can be mounted at a distance from the inverter unit by means of the connector which is integrally forimed with the housing of the test switch, the test switch thus being mountable to portions of the lighting fixture per se or to other structure convenient for access to the test switch for testing purposes.
Accordingly, it is a primary object of the invention to provide a manually operable test switch useful in the testing of an inverter unit installed on a fluorescent lighting fixture to provide emergency lighting capabilities to the fixtures on interruption of normal AC power.
It is another object of the invention to provide a test switch capable of providing a visual test of the operational worthiness of an inverter unit or the like, which switch structures are formed of a minimum of inexpensive parts which can be assembled with relative ease in order to reduce manufacturing expense.
It is a further object of the invention to provide a test switch which causes lamping to be illuminated at reduced levels to indicate the condition of an inverter unit, the test switch structures employing an electrically conductive element displaceable into contact with leads extending from the lamping and which are electrically connected to cables electrically joined to circuitry elements to be tested, a spring-loaded electrical contact being displaced into contact with leads joined to the lamping on manual manipulation of the plunger element against spring loading.
Other objects and advantages of the invention will become more readily apparent in light of the following detailed description of the preferred embodiments.